At 3:15 PM -0800 2/1/02, Tim Rowledge wrote:
>This is the initial report for the VI4 Project group.
>
>Goal: This project is intended to gather together all the vm and vi
>related changes that have been proposed and which require a different
>image format.

One more possible change: It was brought up a few months back that 
the number of object header bits devoted to identity hash (10 or 11 
bits, IIRC) wasn't enough to allow efficient hashed identity 
collections that were very large. It would be nice to have more bits 
for this purpose. On the other hand, I don't really want to increase 
the footprint for small-memory systems, and I don't want to give up 
image portability either, so I'm not sure I really want to propose 
making the header larger.

But we should see if there's anything clever we can do in this area.

Also, as was discussed back then, it would improve things to make the 
identity hash reported by the VM have a larger range than 0-1023, 
even if it can only have 1024 different values. I think I proposed 
multiplying the current value by 65537, a prime number of roughly the 
right magnitude. This wouldn't require an image format change as 
such, but it would require rehashing all existing hashed identity 
collections, including method dictionaries. (I haven't rechecked my 
facts, this is all from memory, so please correct me if I've got any 
of the details wrong.)

There may have been more discussion of this within the last three 
months that I have missed; I've been away from the list until 
recently.

-Martin